The present invention relates to a scanning image display apparatus that displays an image by scanning a light flux from a light source.
As a scanning display apparatus described above, an apparatus has been disclosed in Japanese Patent Laid-Open No. 2005-107456, for example. This scanning display apparatus displays (or projects) an image on a screen using a rotating scanning mirror to two-dimensionally scan a laser beam modulated in accordance with an image signal.
In the scanning image display apparatus that scans the laser beam, the intensity of the laser beam is dispersed over the entire scanning region of the laser beam. Thus, the laser beam requires an intensity by which an image can be displayed in the entire scanning region.
On the other hand, from the viewpoint of the classification of laser products specified by a standard (e.g., JIS C 6802), the illuminance of the laser beam must be equal to or lower than a regulation value at a laser beam exit window (exit aperture) which is provided in a housing of the apparatus and through which the laser beam passes.
Thus, in the apparatus disclosed in Japanese Patent Laid-Open No. 2005-107456, the exit window is provided on a screen at a position where the laser beam enters with an intensity equal to or lower than a certain value.
In conventional scanning image display apparatuses such as one disclosed in Japanese Patent Laid-Open No. 2005-107456, the rotation angle of the scanning mirror, that is a scannable angle of the light flux is fixed.
Thus, in order to change the size of the displayed image, it is necessary that the projection distance from the apparatus to the screen is changed or the light flux from the light source is caused to impinge on the mirror only in part of the rotation angle range of the mirror (i.e., the light flux from is trimmed).
However, it is difficult that the projection distance is changed in some places where the apparatus is provided, which may prevent a desired image size from being obtained. Furthermore, when the rotation angle of the scanning mirror is fixed, only an image having a specific aspect ratio can be displayed.
Furthermore, even when the image size is reduced by the trimming, the rotation angle of the mirror is still wider than an angle at which the light flux is actually scanned for displaying the image. Thus, wasteful power consumption in the scanning unit is caused.
Furthermore, the trimming cuts part of information for the input image signal. Thus, when the image size is changed, the number of displaying pixels is changed. For example, when the image size is reduced, the number of displaying pixels is reduced.